Various fungi such as penicillia molds are the causal agents of the vast majority of losses due to decay in the citrus industry. These organisms attack all varieties of citrus fruit produced from each of the several geographically and climatically diverse citrus growing areas of California and Arizona. Although their greatest impact is felt when completely decayed fruit covered with the sporulating fungus are discovered at the markets, green and blue mold occur, often simultaneously, throughout every phase of postharvest operations. Strategies for the control of these diseases underlie virtually every procedure followed during the normal course of fruit processing and shipping.
This problem has long been a concern in the citrus industry, and has been the subject of early prior art attempts for its remedy. These attempts are set out in various prior art patents including U.S. Pat. Nos. 1,529,461; 2,488,876; 2,374,210; and 2,703,760. These patents are representative of only a few of the prior attempts directed toward the treatment of citrus fruit to eliminate spoilage. Currently, a favorite treating reagent is sodium orthophenylphenate known in the trade as SOPP which ionizes in solution to orthophenylphenol known as OPP.
In the past, treating compositions such as OPP have been brought into contact with fruit in relatively quiescent conditions, such as in the well-known soaking tanks used throughout the industry to immerse the fruit in solutions containing fungicides to thoroughly impregnate the solution and the fungicide, insofar as is possible, into the surface of the fruit. This method has required rather large soaking tanks in which the fruit must be placed for substantial periods of time. Considering the length of time the fruit must be in the soaking tanks, the size of the tanks and the tremendous quantity of fruit that is processed through modern-day packing houses, the soaking technique, while useful, is not cost effective.
Another technique commonly used in the citrus industry for applying coatings to fruit is that of "foaming". In this technique, a coating material including a fungicide, is applied to the fruit in the form of a liquid foam. Because the foam adheres to the surface of the fruit, being formed of high surface tension bubbles usually resulting from the addition of a surfactant, sufficient contact of the fungicide material is made with the skin of the fruit to apply a coating. An example of a foamer for applying the foam is shown in U.S. Pat. No. 2,488,876 to J. F. P. Newhall et al. In modern-day practice, fruit can be conveyed through a foamer washer for its final cleaning prior to packing. In the foamer SOPP is usually applied in the foam at a concentration of about 1% to about 3%. After rinsing and removing excess water, a shipping wax can be applied. However, there are problems with this prior art method in that due to the application of the fungicide in the form of a foam, it is desirable that the foam remain on the fruit in a somewhat quiescent condition to permit thorough wetting of the fruit surface. Thus, in the foaming technique, a relatively small amount of liquid is applied to the fruit and such liquid may not effectively treat the fruit and, because of its small amount, may not carry away dirt and debris that remain on the fruit. Moreover, the foam material is not recyclable and the foam solution not adhering to the fruit is lost.
U.S. Pat. No. 2,374,209 to Kalmar discusses a drenching operation wherein a solution containing 0.15% by weight of SOPP is flooded over fruit on brushes. However, this is but a secondary treatment with the fruit first having been soaked in a tank in the same SOPP solution.
Sharma, U.S. Pat. No. 2,228,410 discloses the drench treating of fruits and vegetables with a composition including OPP which also includes an oil constituent described as a relatively non-volatile petroleum distillate as an essential part of his treating solution.
Sharma, U.S. Pat. No. 2,054,392, also discloses treatment of fruit with SOPP, but shows no apparatus for such treatment.
It is also known to apply SOPP to fruit by immersion in a soak tank followed by rinsing the fruit with overhead water sprays while the fruit is passing over a brush bed. However, where rinse water is recirculated rind injury may result because the lower pH of the rinse water releases more OPP from the solution.
According to this invention, there is provided a novel method and apparatus for eliminating the noted prior art problems and particularly for applying a fungicide contained in a falling liquid which will respectively be present in quantities to both prevent and retard the growth of fungus, and remove debris from the fruit. Thus, in the novel one step drenching process of this invention which is conducted upon a scrubbing bed, as will be hereinafter described, both the fungicide application and debris removal can be accomplished in a single step. Eliminated, by means of the techniques of this invention, are absolute requirements for large soaking tanks or auxilliary debris removal steps prior to or after, the fungicidal application. The fungicide treating step according to the invention can be a primary treating step, prior to packing of the fruit and may be used without other additional preliminary or secondary fungicide treatments in packing houses.